Greenland Ice Sheet May Vanish Faster Than Thought

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It may take less of an increase in global temperatures to melt
the ice sheet covering Greenland than thought, new research
suggests.

The threshold required to melt the ice completely is in the range
of 1.4 to 5.8 degrees Fahrenheit (0.8 to 3.2 degrees Celsius),
with a best estimate of 2.9 degrees F (1.6 degrees C) above
pre-industrial levels, according to a group of European
researchers.

To put these numbers in perspective, climate scientists say the
Earth's surface has already warmed by more than 1.3 degrees (0.7
degrees C) since the Industrial Revolution, when humans began
pumping out large amounts of greenhouse gases, particularly
carbon dioxide.

The
Greenland ice sheet matters because the ice it contains would
substantially raise seas levels if it melted. Antarctica, too, is
covered in ice and could also become a major source of sea-level
rise. Warming is also expected
to melt other pockets of ice around the world, such as
mountain glaciers, and to raise sea levels by causing water to
expand. (Warmer water takes up more space.)

According to a report in 2007 by the Intergovernmental Panel on
Climate Change (IPCC) — the international body charged with
assessing climate change — the Greenland ice sheet could
contribute 23 feet (7 meters) to sea-level rise if it melted
completely. The IPCC report relies on older estimates for
temperatures needed to melt the Greenland ice sheet.

If humanity managed to limit global warming to 3.6 degrees F (2
degrees C) — a goal
embraced by climate negotiators but one that looks
increasingly unlikely — the Greenland ice sheet would disappear
in 50,000 years, according to the study.

However, the greater the warming, the more rapid the melt; 14.4
degrees F (8 degrees C), which the researchers say equates to a
"business-as-usual scenario of greenhouse gas emissions," would
result in a complete loss in 2,000 years.

"This is not what one would call a rapid collapse," said lead
study researcher Alexander Robinson with the Potsdam Institute
for Climate Impact Research in Germany in a press release issued
by the Institute. "However, compared to what has happened in our
planet's history, it is fast. And we might already be approaching
the critical threshold."

Robinson and colleagues used a new computer simulation to
recalculate the temperature threshold. The study was
published online on Sunday (March 11) in the journal Nature
Climate Change.